An Iowa prosecutor added a child endangerment charge Thursday against a woman suspected of kidnapping her half-sister's newborn and leaving him behind a gas station for more than a day in freezing temperatures.

Kristen Smith, 31, made an initial court appearance on the aggravated misdemeanor charge Thursday and was ordered to remain in custody at the Cedar County Jail in Tipton, Iowa, on a $20,000, cash-only bond.

The FBI said Smith kidnapped her half sister's days-old baby, Kayden Powell, from a southern Wisconsin home on Feb. 6. Federal prosecutors in Wisconsin have charged Smith with kidnapping, which carries the possibility of life in prison, but have yet to take her into federal custody.

Cedar County Attorney Jeffrey Renander said he filed the additional charge against Smith to hold her accountable for "what she did to the baby when she was here in Iowa."

The complaint filed by Renander echoes the allegations spelled out last week by federal investigators.

Authorities say Smith had traveled to the Town of Beloit, Wis., to visit her half sister, Brianna Marshall, who had given birth to Kayden on Feb. 1. Early Feb. 6, Marshall woke up to find the baby missing from his bassinet and called 911. Smith had left the home, and an FBI complaint says she was driving back to her home in Denver.

Police contacted Smith as she was driving through Iowa on Interstate 80 and told her to pull over at the nearest gas station for questioning. An officer met her at the Kum & Go in West Branch, finding baby clothing, a car seat and stroller in her car but no sign of Kayden. Smith denied knowledge of the baby's whereabouts but was taken into custody on an outstanding arrest warrant from Texas charging her with tampering with government records.

About 29 hours later, West Branch police chief Mike Horihan found Kayden behind a BP gas station, 500 yards from where Smith had been arrested. The baby was wrapped in blankets inside a plastic storage crate -- alive and well despite temperatures that had dipped below zero.

"The outside temperatures were below freezing at the time K.P. was located," the complaint said. "After K.P. was found, the defendant admitted she had taken K.P. and had placed him behind the BP gas station and also provided law enforcement with a map of where the baby was found."

Investigators say they found emails and Facebook messages in which Smith falsely claimed to be pregnant or to have given birth and say they found a prosthetic pregnancy belly in her car.

An extradition hearing has been scheduled for Friday on the Texas warrant, but Renander said it was unclear how that might be affected by the new Iowa charge. Authorities in Texas have said they will let the federal case take top priority.

Because they have filed a warrant for Smith's arrest, federal prosecutors could take her out of state custody at any time.